154 DR. F. E. BEDDARD ON 



of a millimetre across. The rostellar region of the scolex is 

 very small in the contracted condition, as is the case with other 

 Ophidian Ichthyotseniids. The suckers look outwards and rather 

 upwards. The length of the scolex is not more than half its 

 breadth. Immediately after the scolex there is a neck in which 

 no segmentation is visible ; it is as wide as the scolex, and the 

 body rapidly attains to its greatest width, there being thus no 

 long and thin anterior region. 



The segments become elongated as they mature, and attain to a 

 length of four or five times their breadth, or even perhaps rather 

 more. In this species, as in others of the genus, the genital pores 

 alternate in position from side to side of the body, and the rela- 

 tive positions of the cirrus-sac and vagina also alternate. 



The calcai-eoiis bodies in this species are very abundant ; they 

 extend into the neck region, where they are very plain, in trans- 

 verse sections, forming a layer in the cortical parenchyma, not 

 very far below the subcuticular layer. They are also apparent in 

 the scolex. I have frequently observed in posterior segments of 

 the body that the centre of the calcareous bodies is deep black, 

 due to pigment. In sections through the scolex the four suckers 

 are seen to occupy nearly the whole of the area available, there 

 being but little space between them. The thickness of the 

 suckers is much greater actually and relatively than in the allied 

 Acanthotcenia, which I have recently described *. An examina- 

 tion of these sections failed to show any spiny covering of the 

 body round or in the suckers such as is so conspicuous in Acan- 

 thofmnia. I am convinced that such a spiny covering is entirely 

 absent. 



Sections through the scolex also show the slender muscular 

 fibres which effect the movements of the latter. These fibres do 

 not form bundles, but pervade singly the region lying between 

 the suckers. I have pointed out in a previous communication t 

 that the stout muscles of the suckers in the genus Acanthotcenia 

 concentrate themselves in the neck into very marked and thick 

 bundles of rather thick fibres, which are continued back for a 

 short distance only. It appeared to me when comparing that 

 genus with Ichthi/otcenia, that Acanthotcenia was to be probably 

 distinguished from Ichthyotcenia by, inter alia, this presence of a 

 thick layer of longitudinal muscles in the neck and hj the absence 

 of such a layer in the trunk region, this latter layer being present 

 in Ichthyotcenia. The examination of the species which forms 

 the subject of the present memoir confirms that opinion ; for in 

 Ichthyotcenia gcibonica I have not been able to detect a longi- 

 tudinal layer of fibres in the neck region ; the slender fibres 

 already referred to which effect the movements of the suckers 

 do not become concentrated in the neck into a thick series of 

 bundles as in Accmthotcenia ; nor indeed could I discover any 

 layer at all of such muscles in this part of the body. 



* P. Z. .S. 1913, p. 8, text-fig. 1. 

 t P. Z. S. 1913, p. 9, text-fig. 2. 



